The effects of piperonyl butoxide, a widely used insecticidal synergist, on microsomal enzyme induction will be studied. Since piperonyl butoxide inhibits drug metabolism, the relationship of metabolism of inducers to enzyme induction will be determined. Additionally, the effects of piperonyl butoxide on the metabolism and tissue distribution of several carcinogens will be studied. These effects will be correllated will effects of piperonly butoxide on tumor induction by chemical carcinogens and on the in vivo metabolism of carcinogens.